Aromatic cyanate ester silane coupling agents

ABSTRACT

A composition of matter comprises an aromatic cyanate ester silane comprising at least one cyanate ester group and at least one hydrolyzable silyl group. In the presence of a cyanate ester resin the aromatic cyanate ester silane acts as a coupling agent to improve the adhesion of the cyanate ester to a substrate. The curable compositions are useful as reinforced composites, and as adhesive and coating compositions.

FIELD OF THE INVENTION

This invention relates to novel aromatic cyanate ester silanes whichcontain aromatic cyanate ester groups and hydrolyzable silyl groups.Curable compositions comprising a cyanate ester resins and the aromaticcyanate ester silane as a coupling agent provide adhesives andprotective coatings.

BACKGROUND OF THE INVENTION

Cyanate ester resins have utility in a variety of composite, adhesive,and coating applications, such as circuit board laminates, conductiveadhesives, structural adhesives, protective coatings, aerospacestructures, filled molded parts, structural composites, andsemiconductor encapsulants, where adhesion between the cyanate esterresin and a surface is of critical importance.

Adhesion of polymers to substrates has long been a problem in adhesiveand coating chemistry and in making of polymer composites. One solutionhas been the use of silane coupling agents as described, for example, byPlueddemann in the book "Silane Coupling Agents," published in 1982 byPlenum (New York), pp. 1-28. Typically, silane coupling agents have thestructure X--Y--SiZ₃ where X is a functional group capable ofinteracting, or preferably, reacting, with the polymeric resin, Y is anorganic linkage, and at least one Z is a reactive or hydrolyzable groupcapable of reacting with hydroxyl groups on the surface of thesubstrate. The X group bonds with the polymer network and the SiZ₃ groupbonds to the substrate. This provides a chemical link (covalent bonds)from the polymer to the substrate through the organic group Y andthereby improves the adhesion of the polymer to the substrate. Numeroussilane coupling agents have been developed for a variety of polymericresins, but it is believed a silane coupling agent has never beendeveloped specifically for cyanate ester resins.

Existing silane coupling agents have been used with cyanate esterresins. For example, U.S. Pat. Nos. 5,143,785 and 5,330,684 describecyanate ester based conductive adhesives which may incorporate silanecoupling agents where the X group, shown above, is mercapto, epoxy,acrylyl, or amino. A preferred coupling agent may be3-glycidoxypropyltrimethoxysilane which was used exclusively in theexamples of U.S. Pat. No. 5,143,785. Mercapto, hydroxy, and amino groupsare known to react with cyanate esters but may produce undesirable sidereactions and thermally or hydrolytically unstable bonds. Additionally,amino groups react too rapidly with cyanate esters to be of practicalvalue and are catalysts for cyanate ester cure which leads to reducedshelf life for the adhesive. The '684 patent requires that an epoxyresin be present in conductive adhesive composition. Numerous patents,see U.S. Pat. No. 4,797,454, for example, have reported that epoxygroups couple with cyanate ester groups by the formation of oxazolinegroups. However, recent research results reported by Fyfe and coworkers(Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 32, 1994,pp. 2203-2221) show that the reaction of cyanate esters with epoxycompounds is very complex and does not produce oxazoline structures.These researchers report that the direct reaction of cyanate esters andepoxies provides oxazolidinone structures and that this is a minorreaction pathway. This type of complex and inefficient chemistry isundesirable for a coupling agent.

SUMMARY OF THE INVENTION

Briefly, a composition of matter comprises an aromatic cyanate estersilane comprising at least one aromatic cyanate ester and at least onehydrolyzable silyl groups. When present in admixture with a cyanateester resin, the aromatic cyanate ester silane is a coupling agent forthe resin.

In a further aspect, methods for preparing the composition of thepresent invention are described. The aromatic cyanate ester silanecompounds are novel and are prepared from aromatic hydroxyl compoundswhich contain at least one olefinic double bond, which preferably is analiphatic or cycloaliphatic carbon-to-carbon double bond, by acombination of hydrosilation and cyanation reactions.

In yet a further aspect, a method of coupling a cyanate ester resin to asubstrate by means of the aromatic cyanate ester silane coupling agentof the invention is described.

In a still further aspect, an adhesive film which optionally can includeconductive particles, and which includes the curable composition ofmatter of the present invention comprises a cyanate ester resin and anaromatic cyanate ester coupling agent as well as a thermoplasticpolymer.

In this application:

"cyanate ester" means a derivative of cyanic acid (HOCN) in which the His replaced by an organic group, preferably an aromatic group;

"silane" means a silicon containing compound having at least one singlebond between the silicon atom and a carbon atom of an organic group; and

"hydrolyzable silyl group" means a silicon atom and its substituents,whereby at least one and up to three of the substituents may be cleavedby water or alcohol to produce one to three OH groups attached to thesilicon.

The novel coupling agents of the present invention provide a means bywhich cyanate ester resins can have improved adhesion to inorganic ororganic surfaces. The resulting curable compositions can have utility inreinforced composites and in a variety of adhesive and coatingapplications, such as circuit board laminates, conductive adhesives,structural adhesives, structural composites, protective coatings,aerospace structures, filled molded articles, and semiconductorencapsulants. In these applications adhesion between the cyanate esterresin and an substrate is of critical importance.

It has now been discovered that silane coupling agents incorporatingaromatic cyanate ester groups and hydrolyzable silyl groups can beprepared and that they improve the adhesion of cyanate ester resins tosubstrates.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a micrograph (9.5×enlarged) showing a 3M test chip bonded,using a composition of the present invention, to an indium-tin oxideglass substrate;

FIG. 2 is a micrograph (9.5×enlarged) showing a 3M test chip bonded,using a comparative composition, to an indium-tin oxide glass substrate.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The silane coupling agents of the present invention can be prepared fromaromatic hydroxyl compounds which contain at least one olefinic doublebond by two different methods.

Method A comprises first reacting an aromatic hydroxyl compound whichcontains at least one olefinic double bond with cyanogen halide and abase to give an aromatic cyanate ester compound which contains at leastone olefinic double bond. The aromatic cyanate ester compound whichcontains at least one olefinic double bond can then be hydrosilated togive the aromatic cyanate ester silane coupling agents of the presentinvention.

Method B comprises first hydrosilating an aromatic hydroxyl compoundwhich contains at least one olefinic double bond to give an aromatichydroxyl compound which contains at least one silyl group. The aromatichydroxyl compound which contains at least one silyl group can then bereacted with cyanogen halide and a base to give the aromatic cyanateester silane coupling agent of the present invention.

The hydrosilation reaction is typically carried out in the presence of asuitable catalyst and may be carried out with or without solvent asdescribed by Speier in "Advances in Organometallic Chemistry," Volume17, Academic Press Inc., pp. 407-447, 1979. The reaction is usuallyconducted from -40° C. to about 150° C., preferably from about -20° C.to about 120° C., more preferably from about 0° C. to about 80° C.Suitable catalysts for the hydrosilation reaction include, but are notlimited to, chloroplatinic acid,bis(divinyltetramethyidisiloxane)platinum,tris(triphenylphosphine)rhodium chloride, platinum on carbon, andcolloidal platinum metal. Bis(divinyltetrarnethyidisiloxane)platinum,chloroplatinic acid, and platinum on carbon are the preferred catalysts.

Silanes, which comprise at least one Si--H group, which can be used inthe hydrosilation reaction to prepare the coupling agents of thisinvention, can have the general formula

    H.sub.a R.sub.b SiZ.sub.{4-(a+b)}

where H is a hydride group directly bound to the silicon (Si) atom, a=1to 3, preferably 1 or 2, most preferably 1, R is a nonfunctionalizedalkyl or aromatic group, b=0 to 2, preferably 0 or 1, with the provisothat a+b is less than or equal to 3, and at least one Z is ahydrolyzable group capable of reacting with a hydroxyl group preferablyon a substrate. It is understood that the hydrolyzable group can reactdirectly with a hydroxyl group or its hydrolysis product can react witha hydroxyl group. The hydrolyzable groups are typically halogen oralkoxy groups, and --Cl, --OCH₃, or --OCH₂ CH₃ are the preferredhydrolyzable groups. Illustrative examples of the silanes useful in thehydrosilation reaction leading to the coupling agents of this inventioninclude, trichlorosilane, triethoxysilane, trimethoxysilane,dimethylchlorosilane, dimethylethoxysilane, ethyldichlorosilane,dichloromethylsilane, cyclohexyldichlorosilane,cyclopentyldichlorosilane, dichlorosilane, diisopropylchlorosilane,hexadecyldichlorosilane, hexyldichlorosilane, hexyldimethoxysilane,isobutyldiethoxy silane, methyidiethoxysilane, methyldimethoxysilane,and phenyidichlorosilane. Triethoxysilane, trimethoxysilane, andtrichlorosilane are preferred silanes for the preparation of thecoupling agents of this invention by hydrosilation reactions.

The aromatic hydroxyl compounds which comprise at least one olefinicdouble bond or at least one silyl group can be converted to a cyanateester compound by reaction with preformed cyanogen halide or in situformed cyanogen halide in the presence of a base as described, forexample, by Martin and Bauer in Organic Syntheses, Volume 61, pp. 35-38,1983. The reaction is conducted at a temperature between about -60° C.to about 60° C., preferably from about -10° C. to 10° C. for a timesufficient to complete the reaction, usually from about 0.1 to 10 hours,preferably from about 0.2 to about 5 hours, and more preferably fromabout 0.2 to 2 hours. The reaction is usually carried out in thepresence of a suitable solvent such as, for example, toluene, methylenechloride, tetrahydrofuran, dichloroethane, acetonitrile, diethyl ether,glyme, and combinations thereof Methylene chloride is a preferredsolvent. Tertiary amines are typically used as the base in the reaction,although other bases may be used. Triethyl amine is a preferred base. Ina typical reaction, the aromatic hydroxyl compound and an excess of thecyanogen halide are dissolved in methylene chloride and cooled to thepreferred temperature range. Triethyl amine is then slowly added,usually through an addition funnel in a dropwise manner, such that thetemperature of the reaction solution does not exceed the preferredrange. After further stirring, the reaction is quenched with water andthe cyanate ester product is isolated by standard chemical techniques.

Suitable aromatic hydroxyl compounds which can be employed in thismethod to prepare silane coupling agents containing cyanate esterfunctional groups of the present invention include any compoundcontaining at least one aromatic hydroxyl group per molecule and also atleast one straight chain or branched aliphatic or cycloaliphaticcarbon-to-carbon double bond per molecule. Such aromatic hydroxylcompounds include, but are not limited to, those represented by thegeneral formula

    HO--Ar--U

wherein Ar can be a single aromatic ring, or it can be two or more fusedaromatic rings or two or more aromatic rings connected by at least oneof a) a carbon-carbon single bond, b) a hydrocarbyl group, c) an ethergroup, or d) a thioether group; Ar can comprise 5 to 30 carbon atoms andzero to five O, N, S, and P heteroatoms; HO can be one or more hydroxylgroups directly bound to one of the aromatic rings of Ar; and U can beat least one olefinically unsaturated straight chain or branchedaliphatic or olefinically unsaturated cycloaliphatic group having 2 to30 carbon atoms directly bound to one of the aromatic rings of Ar. TheAr group may further contain organic substitutents such as alkyl,alkoxy, halo, ester, sulfide, and ketone groups provided these groups donot interfere with the synthesis or use of the coupling agents of thisinvention. The U group may contain ether, thioether, ester, or ketonelinkages or other organic substituents provided these linkages ororganic substituents (which substituents can also include halo atoms) donot interfere with the synthesis or use of the coupling agents of thisinvention. Examples of Ar groups include benzene, naphthalene,2,2-diphenylpropane, diphenyl ether, and biphenyl. Examples of U groupsinclude vinyl, allyl, --O--CH═CH₂, --O--CH₂ --CH═CH₂, cyclohexenyl,cyclopentenyl, and --CH₂ --(CH₂)_(x) --CH═CH₂ where x can be an integer1-5.

Illustrative examples of aromatic hydroxyl compounds containingaliphatic or cycloaliphatic carbon-to-carbon double bonds include2-allylphenol, 4-allylphenol (also called 4-(2-propenyl)phenol),4-propenylphenol, 4-hydroxystyrene, the monoallylether of bisphenol A,4-allyl-2-methoxyphenol (also called eugenol), 2-propenylphenol,2-methoxy-4-propenylphenol (also called isoeugenol),2-ethoxy-5(1-propenyl)phenol, and 4-allyl-2,6-dimethoxyphenol.

Generally, for each equivalent of the aromatic hydroxyl compoundcontaining olefinic unsaturation it is preferred to use excess amountsof the other reactants in preparing the aromatic cyanate ester silanecoupling agents of the invention.

The ability to synthesize the coupling agents of this invention wassurprising. The hydrosilation reaction requires transition metalcatalysts, some of which are organometallic compounds, and it is wellknown, as described in U.S. Pat. No. 5,215,860, for example, that suchmaterials are also catalysts for the cyclotrimerization of cyanate estergroups. Thus, the catalytic hydrosilation of olefinic double bonds incompounds which also contain cyanate ester groups could be expected tocause the cyclotrimerization of the cyanate ester groups. In such acase, the resulting triazine would not be effective as a coupling agent.The conversion of aromatic hydroxyl groups to cyanate ester groups byreaction with cyanogen halide typically requires aqueous conditions inthe isolation of the product. Additionally, the reaction is oftencarried out in a two-phase system where one phase is aqueous asdescribed in the Martin and Bauer reference cited previously. Thus,reaction of an aromatic hydroxyl compound which also containshydrolyzable silane (SiZ as disclosed above) groups with cyanogen halideunder typical conditions would be expected to result in the hydrolysisof the silane groups. This would provide a complex mixture of productswhich could not readily be separated or purified. Additionally,significant amounts of, for example, alcohol or hydrochloric acid couldbe produced in the hydrolysis reaction depending on the nature of thehydrolyzable silane groups. Alcohols and acids are known to react withcyanate ester groups and their presence could adversely affect thestability of the desired coupling agent product. Surprisingly, themethods of the present invention can provide the desired coupling agentisolatable as a pure compound despite undesirable side reactions.

Method A of the preparation of the coupling agents of this invention canfollow the steps of a) providing an aromatic hydroxyl compound whichcontains at least one aliphatic or cycloaliphatic carbon-to-carbondouble bond, b) reacting the aromatic hydroxyl compound with cyanogenhalide and a base where a preferred reaction temperature between -10° C.and 10° C. is maintained, and c) reacting the resulting cyanate estercompound with a silane containing both Si--H bonds and hydrolyzablegroups in the presence of a hydrosilation catalyst where a preferredreaction temperature below 100° C. is maintained. Hydrolyzable groupssuch as methoxy, ethoxy, or chloro are required so that the resultingaromatic cyanate ester silane will be a coupling agent.

Illustrative of a Reaction Scheme for Method A is as follows: ##STR1##wherein Z is as defined above.

Method B of the preparation of the coupling agents of this invention canfollow the steps of a) providing an aromatic hydroxyl compound whichcontains at least one aliphatic or cycloaliphatic carbon-to-carbondouble bond, b) reacting the aromatic hydroxyl compound with a silanecontaining both Si--H bonds and hydrolyzable groups in the presence of ahydrosilation catalyst where a preferred reaction temperature below 100°C. is maintained, and c) reacting the resulting aromatic hydroxylcompound which contains at least one silyl group with cyanogen halideand a base where a preferred reaction temperature between -10° C. and10° C. is maintained. Hydrolyzable groups on silicon, as noted above,are required so that the resulting aromatic cyanate ester silane will bea coupling agent.

Illustrative of a Reaction Scheme for Method B is as follows: ##STR2##wherein Z is as defined above.

The coupling agents of this invention prepared by the above methods canhave the general formula

    {(NCO).sub.c --Ar--U'--}.sub.a SiR.sub.b Z.sub.{4-(a+b)}

where Ar is as described above, NCO is a cyanate group directly bound toan aromatic ring of Ar, c can be an integer 1 to 5, preferably 1 or 2,U' is an organic group resulting from the hydrosilation of the group Udescribed above, a can be an integer 1 to 3, preferably 1 or 2, mostpreferably 1, R can be as described above, b can be 0 or 1 or 2preferably 0 or 1, with the proviso that a+b is less than or equal to 3,and Z is as described above. Examples of U' groups resulting from thehydrosilation of the U groups described above include ethylene,propylene, --O--CH₂ --CH₂ --, --O--CH(CH₃)--, --O--CH₂ --CH₂ --CH₂ --,--O--CH₂ --CH(CH₃)--, cyclohexylene, cyclopentylene, --CH₂ --(CH₂)_(x)--CH₂ --CH₂ -- where x=1-5, and --CH₂ --(CH₂)_(x) --CH(CH₃)-- where xcan be 1-5.

Illustrative examples of the coupling agents of this invention include3-(4-cyanatophenyl)propyltrimethoxysilane,3-(2-cyanatophenyl)propyltrimethoxysilane,3-(4-cyanatophenyl)propyltriethoxysilane,3-(4-cyanatophenyl)propyltrichlorosilane,3-(2-cyanatophenyl)propyltriethoxysilane,3-(2-cyanatophenyl)propyltrichlorosilane,3-(3-cyanatophenyl)propyltriethoxysilane,3-(3-cyanatophenyl)propyltrichlorosilane,3-(3-cyanatophenyl)propyltrimethoxysilane,2-trimethoxysilyl-1-(4-cyanatophenyl)propane,2-triethoxysilyl-1-(4-cyanatophenyl)propane,2-trichlorosilyl-1-(4-cyanatophenyl)propane,2-trimethoxysilyl-1-(2-cyanatophenyl)propane,2-triethoxysilyl-1-(2-cyanatophenyl)propane,2-trichlorosilyl-1-(2-cyanatophenyl)propane2-triethoxysilyl-1-(3-cyanatophenyl)propane,2-trichlorosilyl-1-(3-cyanatophenyl)propane,2-trimethoxysilyl-1-(3-cyanatophenyl)propane,1,1-trimethoxysilyl(4-cyanatophenyl)propane,1,1-triethoxysilyl(4-cyanatophenyl)propane,1,1-trichlorosilyl(4-cyanatophenyl)propane,1,1-trimethoxysilyl(2-cyanatophenyl)propane,1,1-triethoxysilyl(2-cyanatophenyl)propane,1,1-trichlorosilyl(2-cyanatophenyl)propane,1,1-triethoxysilyl(3-cyanatophenyl)propane,1,1-trichlorosilyl(3-cyanatophenyl)propane,1,1-trimethoxysilyl(3-cyanatophenyl)propane,2-(4-cyanatophenyl)ethyltrimethoxysilane,2-(4-cyanatophenyl)ethyltriethoxysilane,2-(4-cyanatophenyl)ethyltrichlorosilane,2-(2-cyanatophenyl)ethyltrimethoxysilane,2-(2-cyanatophenyl)ethyltriethoxysilane,2-(2-cyanatophenyl)ethyltrichlorosilane,2-(3-cyanatophenyl)ethyltriethoxysilane,2-(3-cyanatophenyl)ethyltrichlorosilane,2-(3-cyanatophenyl)ethyltrimethoxysilane,1-(4-cyanatophenyl)ethyltrimethoxysilane,1-(4-cyanatophenyl)ethyltriethoxysilane,1-(4-cyanatophenyl)ethyltrichlorosilane,1-(2-cyanatophenyl)ethyltrimethoxysilane,1-(2-cyanatophenyl)ethyltriethoxysilane,1-(2-cyanatophenyl)ethyltrichlorosilane,1-(3-cyanatophenyl)ethyltriethoxysilane,1-(3-cyanatophenyl)ethyltrichlorosilane,1-(3-cyanatophenyl)ethyltrimethoxysilane,4-(3-trimethoxysilylpropyl)-2-methoxyphenylcyanate,4-(2-trimethoxysilylpropyl)-2-methoxyphenylcyanate,4-(1-trimethoxysilylpropyl)-2-methoxyphenylcyanate,4-(3-triethoxysilylpropyl)-2-methoxyphenylcyanate,4-(2-triethoxysilylpropyl)-2-methoxyphenylcyanate,4-(1-triethoxysilylpropyl)-2-methoxyphenylcyanate,4-(3-trichlorosilylpropyl)-2-methoxyphenylcyanate,4-(2-trichlorosilylpropyl)-2-methoxyphenylcyanate,4-(1-trichlorosilylpropyl)-2-methoxyphenylcyanate,4-(3-trimethoxysilylpropyl)-2,6-bis(methoxy)phenylcyanate,4-(2-trimethoxysilylpropyl)-2,6-bis(methoxy)phenylcyanate,4-(3-triethoxysilylpropyl)-2,6-bis(methoxy)phenylcyanate,4-(2-triethoxysilylpropyl)-2,6-bis(methoxy)phenylcyanate,4-(3-trichlorosilylpropyl)-2,6-bis(methoxy)phenylcyanate,4-(2-trichlorosilylpropyl)-2,6-bis(methoxy)phenylcyanate,4-(2-trimethoxysilylpropyl)-2-ethoxyphenylcyanate,4-(1-trimethoxysilylpropyl)-2-ethoxyphenylcyanate,4-(2-triethoxysilylpropyl)-2-ethoxyphenylcyanate,4-(1-triethoxysilylpropyl)-2-ethoxyphenylcyanate,4-(2-trichlorosilylpropyl)-2-ethoxyphenylcyanate,4-(1-trichlorosilylpropyl)-2-ethoxyphenylcyanate, 2,2-4-(3-trimethoxysilylpropoxyphenyl)!(4'-cyanatophenyl)propane, 2,2-4-(2-trimethoxysilylpropoxyphenyl)!(4'-cyanatophenyl)propane, 2,2-4-(3-triethoxysilylpropoxyphenyl)!(4'-cyanatophenyl)propane, 2,2-4-(2-triethoxysilylpropoxyphenyl)!(4'-cyanatophenyl)propane, 2,2-4-(3-trichlorosilylpropoxyphenyl)!(4'-cyanatophenyl)propane, 2,2-4-(2-trichlorosilylpropoxyphenyl)!(4'-cyanatophenyl)propane,4'-(3-trimethoxysilylpropoxy)-4-biphenylcyanate,4'-(3-triethoxysilylpropoxy)-4-biphenylcyanate,4'-(3-trichlorosilylpropoxy)-4-biphenylcyanate,4'-(2-trimethoxysilylpropoxy)-4-biphenylcyanate,4'-(2-triethoxysilylpropoxy)-4-biphenylcyanate,4'-(2-trichlorosilylpropoxy)-4-biphenylcyanate,4-cyanatophenyl-4'-(3-trimethoxysilylpropoxyphenyl)sulfone,4-cyanatophenyl-4'-(3-triethoxysilylpropoxyphenyl)sulfone,4-cyanatophenyl-4'-(3-trichlorosilylpropoxyphenyl)sulfone,4-cyanatophenyl-4'-(2-trimethoxysilylpropoxyphenyl)sulfone,4-cyanatophenyl-4'-(2-triethoxysilylpropoxyphenyl)sulfone, and4-cyanatophenyl-4'-(2-trichlorosilylpropoxyphenyl)sulfone.

The coupling agents of this invention can be used in conjunction withcyanate ester resins to improve the adhesion of the cured resin tosubstrates. In one embodiment, the coupling agent may be incorporatedinto the cyanate ester formulation as an additive which improvesadhesion to isubstrates upon curing of the cyanate ester formulation.Alternatively, the coupling agent may be used to treat the surface ofthe substrate as, for example, a primer. The cyanate ester formulationmay then be coated onto the primed substrate and cured to give a coatingwith improved adhesion.

Polyfunctional cyanate ester resins that are useful in the practice ofthe present invention preferably have the general formula

    Q(OCN).sub.p

where p can be an integer from 2 to 7, and wherein Q can comprise a di-,tri-, or tetravalent aromatic hydrocarbon containing from 5 to 30 carbonatoms and zero to 5 aliphatic, cyclic aliphatic, or polycyclicaliphatic, mono- or divalent hydrocarbon linking groups containing 7 to20 carbon atoms. Optionally, Q may further comprise 1 to 10 heteroatomsselected from the group consisting of nonperoxidic oxygen, sulfur,non-phosphino phosphorus, non-amino nitrogen, halogen, and silicon. Thecyanate ester resins may be in the form of monomers, such as2,2-bis(4-cyanatophenyl)propane which is commercially available asAroCy™ B-10 from Ciba Matrix Resins, Hawthorne, N.J., or cyanateoligomers. Partially cyclotrimerized oligomers, such as AroCy™ B-30 orB-50 (Ciba) where approximately 30 and 50% of the cyanate ester groupsof AroCy™ B-10 have been cyclotrimerized can be used. Cyanated novolacresins such as Primaset™ PT-30, PT-60, and PT-90, all commerciallyavailable from Allied-Signal Inc., Morristown, N.J., are also useful inthe practice of the present invention. Polyaromatic cyanate ester resinscontaining polycyclic aliphatic diradicals such as Quatrex™ 7187 (DowChemical, Midland, Mich.) are also useful in the practice of the presentinvention. Other commercially available cyanate ester resins includeAroCy™ M-10, M-20, M30, M-50, L-10, XU-366, XU-371, and XU-378, allavailable from Ciba Matrix Resins and Skylex™ resins available fromMitsubishi Gas Chemical Co., Inc., Tokyo. Examples of cyanate estermonomers include: 1,3- and 1,4-dicyanatobenzene,2-tert-butyl-1,4-dicyanatobenzene, 2,4-dimethyl-1,3-dicyanatobenzene,2,5-di-tert-butyl-1,4-dicyanatobenzene,tetramethyl-1,4-dicyanatobenzene, 4-chloro-1,3-dicyanatobenzene,1,3,5-tricyanatobenzene, 2,2'- or 4,4'-dicyanatobiphenyl,3,3',5,5'-tetramethyl-4,4'-dicyanatodiphenyl, 1,3-, 1,4-, 1,5-, 1,6-,1,8-, 2,6-, or 2,7-dicyanatonaphthalene, 1,3,6-tricyanatonaphthalene,bis(4-cyanatophenyl)methane, bis(3,5-dimethyl-4-cyanatophenyl)methane(AroCy™ M-10), 2,2-bis(4-cyanato-phenyl)propane (AroCy™ B-10),1,1,1-tris(4-cyanatophenyl)ethane, 1,1-bis(4-cyanatophenyl)ethane(AroCy™ L-10), 2,2-bis(3,5-dichloro-4-cyanatophenyl)propane,2,2-bis(3,5-dibromo-4-cyanatophenyl)propane, bis(4-cyanatophenyl)ether,4,4'-(1,3-phenylenediisopropylidene)diphenylcyanate (AroCy™ XU-366),bis(4-cyanato-phenyl)ketone, bis(4-cyanatophenyl)thioether,bis(4-cyanatophenyl)sulfone, tris(4-cyanatophenyl)phosphite, andtris(4-cyanatophenyl)phosphate. Essentially any di- or polyfunctionalphenolic compound which reacts with cyanogen halide in the presence of abase to form a di- or polyfunctional aromatic cyanate ester compound maybe useful in the present invention.

Monofunctional cyanate ester compounds such as phenylcyanate,4-cumylphenylcyanate, 4-t-butylphenylcyanate, and 4-phenylphenylcyanatemay also be incorporated into the cyanate ester formulations. The use ofmonofunctional cyanate esters in combination with polyfunctional cyanateester resins can lower crosslink density in the cured resin and providecured compositions with enhanced flexibility.

Curing agents useful in the practice of the present invention may bechosen from those known in the art. Representative useful curing agentsinclude strong Lewis acids such as AlCl₃ and BF₃, protonic acids such asHCl and H₃ PO₄, amines such as triethylamine and 1,4-diazabicyclo2.2.2!octane, metal salts of carboxylic acids such as tin octoate andzinc naphthenate, and various other materials such as sodium hydroxide,phosphines, phenols, imidazoles, metal acetylacetonates, organicperoxides, carboxylic acid anhydrides, organic azo compounds.Organometallic compounds, that is compounds containing at least onetransition metal atom to carbon atom covalent bond, are also usefulcuring agents for cyanate ester resins and are described in U.S. Pat.No. 5,215,860. Curing is accomplished in the presence of energy,generally heat optionally in the presence of light, preferably at atemperature in the range 60 to 300° C., more preferably 100 to 200° C.

A composition of matter of the present invention preferably comprises anaromatic cyanate ester silane comprising at least one cyanate estergroup and at least one alkoxysilyl group. The composition optionallyfurther comprises a cyanate ester resin. In the presence of a substratethe aromatic cyanate ester silane functions as a coupling agent for thecyanate ester resin. The curable compositions are useful as composite,adhesive and coating compositions. Typically the solvent-freecompositions have a cure time less than 300 seconds at a temperature of180° C. when the amount of the cyanate ester curing agent, as disclosedabove, is in the range of from 0.1 to 5% by weight. The amount ofcoupling agent can be in the range of more than 0 and up to 15 partscoupling agent to 100 parts cyanate ester resin, preferably 1 to 5 partscoupling agent per hundred parts resin.

Substrates suitable in the practice of this invention which can beinorganic or organic substrates may take essentially any physical shape.They may, for example, be substantially flat surfaces such as glassplate, fine powders such as graphite or fumed silica fillers, fiberssuch as glass reinforcing fibers, or large particles such as glassbubbles or beads. Substrates suitable in the practice of this inventionmay be of essentially any chemical composition provided that the surfaceof the substrate has groups, preferably hydroxyl groups, which arecapable of reacting with the hydrolyzable groups of the coupling agentthereby attaching the Si group to the substrate surface. Illustrativeexamples of substrates suitable in the practice of this inventioninclude glasses such as soda lime glass, borosilicate glass, and glasscoated with electrically conductive indium-tin oxide layers; metals ormetalloids with oxide layers such as cadmium, silicon, zinc, aluminum,iron, copper, nickel, tin, brass, steel, and titanium; and ceramics suchas alumina, magnesia, silica, and magnesium silicate.

The cyanate ester formulations of the present invention (coupling agentplus resin and optional adjuvants) can be coated onto, into, orintimately mixed with a substrate to provide coated composites or filledmolded articles to provide coated filled articles.

The cyanate ester formulations may be in the form of monolithicstructures, moldable liquids or solids, dry film adhesives, pressuresensitive adhesives, dispensable liquids, or solvent-borne coatings.

In a preferred embodiment, an adhesive film comprises

(a) 75 to 100 percent by volume of an adhesive component comprising:

(1) 5 to 75 percent by weight of a thermoplastic polymer,

(2) 95 to 25 percent by weight of a cyanate ester resin,

(3) 0.1 to 5 percent by weight of an aromatic cyanate ester silanecoupling agent of the present invention, the coupling agent comprisingat least one hydrolyzable silyl group, and

(4) 0.1 to 5 percent by weight of a catalyst for curing a cyanate esterresin; and

(b) 0 to 25 percent by volume of electrically conductive particles.

Preferably, the film has a cure time of less than 300 seconds at atemperature of 180° C. When conductive particles are present, preferablyin the range of 1 to 25 percent by volume, more preferably in the rangeof 2 to 10 percent by volume, the adhesive film is antisotropicallyconductive adhesive film.

Compositions of the present invention are particularly useful aselectronic adhesives. Electronic adhesives are used to simultaneouslyadhesively bond and electrically interconnect two circuit bearingsubstrates. They may be in the form of liquid adhesives which may bedispensed by any of a number of means, such as screen printing or bysyringe, or they may be film adhesives which may be free standing orplaced on a discardable carrier film. Depending upon the nature of thecircuitry to be bonded, the electronic adhesives may or may not haveparticles of an electrically conductive material dispersed therein. Forexample, electrical contact may be made by metallic features on thesubstrates, such as metallic projections on a "bumped" chip, whichprotrude through the adhesive during the bonding step. Alternatively, afilm adhesive can be loaded with electrically conductive particles suchthat no electrical conductivity is possible in the plane of the film butelectrical conductivity is provided through the thickness of the film.Such films are typically referred to as "z-axis adhesive films" ("ZAF")or "anistropically conductive adhesive films" ("ACF"). These filmadhesives have the ability to establish multiple discrete electricalconnections, often in extremely close proximity, between twomicroelectronic components. Cyanate ester resin containing ZAF materialsmay be made by a variety of methods including solvent casting asdescribed in U.S. Pat. Nos. 5,143,785 and 5,330,684, and solventlessfree radical polymerization as described in the co-pending applicationU.S. Ser. No. 08/078,981. In any case, adhesion of the cyanate estercontaining ZAF to substrates, such as ITO (indium-tin oxide) coatedglass, may be improved by incorporation of the aromtic cyanate estersilane coupling agent as described herein.

In a ZAF material, conductive particles provide multiple discreteinterconnections for each circuit trace or pad. The conductive particlesdesirably can be in a size and loading in accordance with the end useapplication. Factors, such as the width of circuit traces or pads anddistances between adjacent circuit traces or pads can be used todetermine the particle size and volume density. The conductive particlesdesirably can be sufficiently small so as not to span the distancebetween adjacent circuit traces or pads so as to prohibit adjacenttraces or pads from shorting out; and can be present in sufficientnumbers so as to provide multiple discrete contact points at each traceor pad location. Typically, the particle size diameters range from 3 to30 micrometers (μm), and preferably 4-15 μm. Useful conductive particleloadings can be in the range of more than zero to 25% by volume comparedto the adhesive, preferably 0.2-25% by volume, and most preferably 1-10%by volume. For example, a particle population having diameters of 10-15μm and loaded at approximately 1-10% by weight into the adhesivecomposition can provide interconnections for trace sizes as small as100,000 μm² and positioned with as little as 50 μm separation betweenadjacent traces. Any of several particle types can be selected based onthe end use application. Factors such as metallurgy and the hardness ofthe substrate can be used to select the particle type for a givenapplication. Useful conductive particles for ZAF materials include metalparticles, metallized polymer particles, metallized glass particles, andcarbon particles.

Thermoplastics, such as polyvinyl acetal, polysulfones, polyesters,polyamides, polycarbonates, polyethers, and phenoxy resins, aredesirable in solvent cast cyanate ester containing adhesive films andZAF materials as they enhance the film handling characteristics of theresulting material. The thermoplastic can be present at about 5 to 75%by weight, and for a free-standing or transfer adhesive is preferablypresent at about 20 to 60% by weight. In use, substantially solvent-freeZAF material is interposed between the substrates to be connected,circuit traces or pads are aligned, and heat and pressure are applied tocure the ZAF and provide an adhesively bonded and electrically connectedstructure. Typically, the adhesive bond forms in less than 300 secondsat temperatures of 180° C. and pressure of 1.5 megapascals.

Adjuvants such as solvents, thermoplastics, pigments, electricallyand/or thermally conductive particles, abrasive particles, stabilizers,antioxidants, inert fillers, binders, plasticizers, fungicides,bactericides, surfactants, blowing agents, and other additives as isknown to those skilled in the art can be added to the compositions ofthis invention in amounts suitable for their intended purposes.

The cyanate ester formulations may have utility as, for example,insulating electronic adhesives, electrically conductive electronicadhesives, thermally conductive adhesives, structural adhesives,conformal coatings, protective coatings, decorative coatings, binders,and reinforced structural composites.

Objects and advantages of this invention are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention.

EXAMPLES Example 1 Synthesis of 4-(2-propenyl)phenol

To 50.01 g (337.4 mmol) of 1-methoxy-4-(2-propenyl)benzene (AldrichChemical Company, Milwaukee, Wis.) dissolved in 300 mL of anhydrousmethylene chloride was added dropwise 375 mL (375 mmol) of 1.0M borontribromide (Aldrich) in methylene chloride. The reaction was run undernitrogen at room temperature and the mixture was stirred for 1 hour. Themixture was poured over 1000 mL of crushed ice, stirred for 5 minutes,and transferred to a separatory funnel. The organic layer was drainedand saved. The boron salts were transferred to a filter containingCelite™ (Aldrich Chemical Co., Milwaukee, Wis.) and the filtercontaining the salts was washed with portions of methylene chloride andthen water. The filtrate was transferred to a separatory funnel and theorganic and aqueous layers were separated. The aqueous layer wasextracted with four 100-mL portions of methylene chloride. The methylenechloride solutions were pooled, dried over anhydrous magnesium sulfate,and filtered. The solvent was removed under vacuum to yield 25.27 g(56%) of crude 4-(2-propenyl)phenol. The crude product was distilledtwice at reduced pressure to yield 20.34 g (45%) of4-(2-propenyl)phenol. The NMR data was consistent with that reported byRajashekhar and coworkers (J. Biol. Chem. 1984, 259, 6925).

Example 2 Synthesis of 3-(4-cyanatophenyl)propyltrimethoxysilane byMethod A

To a solution of 2.142 g (15.96 mmol) of 4-(2-propenyl)phenol (preparedas in Example 1) in 15 mL of methylene chloride was added 2.351 g (22.19mmol) of cyanogen bromide (Aldrich). The mixture was cooled in anice-salt bath and 3 mL (22 mmol) of triethylamine was added dropwisewith stirring. The mixture was stirred for an additional 15 minutes. Thesolvent was removed under vacuum and the mixture was transferred to aseparatory funnel with 25 mL of water and 75 mL of petroleum ether(30-60° C. boiling range). The aqueous and organic layers wereseparated. The organic layer was washed with three 50 mL portions 6Nhydrochloric and one 50 mL portion of saturated sodium bicarbonate,dried over anhydrous magnesium sulfate, and filtered. The solvent wasremoved under vacuum to yield 1.668 g (66%) of crude1-cyanato-4-(2-propenyl)benzene. The product was distilled to yield1.307 g (51%) of 1-cyanato-4-(2-propenyl)benzene. The structure of theproduct was verified by IR and NMR spectroscopy. The product can befurther purified by passing the product through a silica gel columnusing 1% toluene in petroleum ether as the solvent system.

To 3.94 g (24.75 mmol) of purified 1-cyanato-4-(2-propenyl)benzene,prepared as described above, at 65° C. was added 10 μL of a 3% solutionof Karstedt's™ catalyst (platinum-divinyltetramethyldisiloxane complex)in xylene (United Chemical Technologies, Bristol, Pa.). Trimethoxysilane(Aldrich) was added in 500 μL increments followed by 10 μL increments ofthe catalyst solution until NMR showed that the reaction was more than80% complete. The product was distilled twice to yield 2.94 g (42%) of3-(4-cyanatophenyl)propyltrimethoxysilane. The structure of the productwas verified by IR and NMR.

Example 3

(a) Synthesis of 3-(4-cyanatophenyl)propyltrimethoxysilane) by Method B.To a 100 mL 3-necked round-bottomed flask with a magnetic stirrer andthermometer, open to the atmosphere, was added 9.8 grams 4-allyl phenoland 10.23 mL trimethoxysilane. To this was added 0.03 mL Karstedt'scatalyst (as defined in Example 2). The reaction slowly exothermed to30° C. over a four-minute period. After seven minutes the temperaturedropped to 29° C. and 0.03 mL Karstedt's catalyst was added. The mixtureexothermed to 32° C. in four minutes. After 40 minutes the temperaturedropped to 29° C. and 0.03 mL Karstedt's catalyst was added. The mixtureexothermed to 32° C. and after stirring 35 minutes 0.03 mL Karstedt'scatalyst was added. The mixture was stirred two hours and 15 minutes and0.03 mL catalyst was added. The mixture was stirred 2 hours. ¹ H-NMRshowed no residual starting material. The mixture was transferred to a500 mL 3-necked round-bottomed flask with thermometer and additionfunnel. The product was diluted with 150 mL dichloromethane and 25 gcyanogen bromide was added. The mixture was cooled to 7° C. in an icebath. To this was added 21.38 mL triethylamine dropwise at a rate suchthat the temperature did not go above 10° C. The mixture was stirred fortwo hours. The reaction was filtered through Celite™ and diluted with200 mL dichloromethane. The mixture was extracted two times with water.The organic phase was dried over magnesium sulfate, filtered, and thesolvent was removed in vacuo. The product was kept overnight in thefreezer. The mixture was purified by distillation at reduced pressure togive 2.8 grams of pure 3-(4-cyanatophenyl)propyltrimethoxysilane. Thestructure of the product was confirmed spectroscopically.

(b)Synthesis of 3-(2-cyanatophenyl)propyltrimethoxysilane.

To a 50 mL 3-necked round bottom flask with thermometer, open to theatmosphere, was added 2.0 grams 2-allyl phenol and 1.90 gramstrimethoxysilane. To this was added 0.03 mL Karsteds catalyst (asdefined in Example 2). The reaction was exothermic and an ice bath wasapplied once the temperature rose above 27° C. The temperature reached45° C. and then dropped to 21° C. The temperature was held at 21° C.with no external cooling for 10 minutes. An additional 0.2 mL (0.1equivalents) trimethoxysilane was added and 0.005 mL Karsteds catalyst.The reaction was slightly exothermic and bubbled. After a total reactiontime of 2 hours and 45 minutes proton NMR showed the desired product tobe present with no remaining starting material. The reaction was dilutedwith 30 mL dichloromethane and 5.0 grams cyanogen bromide was added. Themixture was cooled in an ice bath to 5° C. Triethylamine (4.36 mL) wasadded dropwise at such a rate that the temperature remained at 10° C.The total addition time was 15 minutes. The mixture was then stirred anadditional 10 minutes at 5° C. and the cooling bath was removed. Theresulting mixture was stirred at room temperature for one hour and 15minutes. The mixture was diluted with 50 mL dichloromethane andextracted two times with 50 mL portions of water. The organic phase wasdried over magnesium sulfate, filtered, and the solvent was removed invacuo. The product was distilled using an aspirator vacuum of 15 mm Hgto remove the triethyl amine. The product was distilled at reducedpressure to give a fraction that contained approximately 50% of3-(2-cyanatophenyl)propyltrimethoxy silane. The structure of the productwas confirmed spectroscopically.

Example 4

Plain glass microscope slides were utilized to test the silane couplingagent. Three slides (comparative) were dipped in a 1% solution of3-glycidoxypropyltrimethoxysilane in ethanol; three slides were dippedin a 1% solution of 3-(4-cyanatophenyl)propyltrimethoxysilane (fromExample 3) in ethanol; and three slides (comparative) were leftuntreated. The treated slides were allowed to dry. The cyanate esterAroCy B-30 was heated in an oven to 65° C. until it flowed easily and0.25% by weight cyclopentadienyl iron dicarbonyl dimer catalyst wasadded and thoroughly mixed. Approximately 0.3 g of the catalyzed AroCyB-30 mixture was placed on each of the nine slides described above andthese were placed in a 180° C. oven for ten minutes. Upon cooling, theslides were placed in a water bath which was maintained at 65° C. andstirred slowly to ensure circulation of the water. The bath wasmonitored periodically and the slides were removed and evaluated.Evaluation consisted of applying light to moderate pressure with the tipof a scalpel blade at the edge of the adhesive-glass interface. Failurewas indicated by the clean removal of the adhesive from the glass.Slides that did not fail were returned to the bath. It was observed thatthe blank or untreated slides failed within 1 hour. The slides treatedwith 3-glycidoxypropyltrimethoxysilane failed when tested after 20hours. The slides treated with 3-(4-cyanatophenyl)propyltrimethoxysilanefailed after 192 hours.

Example 5

Two formulations were prepared using the proportions in Table 1. Thecyanate ester and the polyvinylacetal were dissolved in methyl ethylketone, followed by addition of the cyanate silane coupling agent, themanganese acetylacetonate catalyst which was dissolved in methyl ethylketone, and the gold-plated conductive particles, all being added andmixed into the solution. The dispersion was stirred until uniform. Acomparative sample was prepared with an epoxy silane coupling agent inplace of the cyanate silane. These dispersions were coated onto asilicone-treated PET film using a knife coater and dried for 10 minutesat 40° C. The thickness of the adhesives was about 25 microns.

                  TABLE 1    ______________________________________                  Parts (by weight)    Component       Example 5 Comparative Example 5    ______________________________________    Cyanate ester.sup.1                    60        60    Polyvinylacetal.sup.2                    40        40    Cyanate silane coupling agent.sup.3                    2         0    Epoxy silane coupling agent.sup.4                    0         2    (comparative)    Manganese acetylacetonate.sup.5                    1         1    Au/Ni/benzoguanamine-resin                    12.5      12.5    conductive particles.sup.6    Methyl ethyl ketone                    170       170    ______________________________________     .sup.1 BT2160RX ™ from Mitsubishi Gas Chemical Co., Inc.     .sup.2 SLec KS1 ™ from Sekisui Chemical Co., Ltd.     .sup.3 3(4-cyanatophenyl)propyltrimethoxysilane     .sup.4 3glycidoxypropyltrimethoxysilane     .sup.5 C.sub.15 H.sub.21 O.sub.6 Mn from Dojindo Laboratories     .sup.6 20GNR4.6 EH ™ from Nippon Chemical Industrial Co., Ltd.

The adhesive film was peeled off the liner and placed onto the glasssubstrate on a bonding stage. A 3M 120 test chip was attached to thethermode of the bonder. The chip was then applied to the glass substratewith bonding accomplished by use of a pulse heat bonder with a bond timeof 2 minutes at 180° C. under 15 kg/cm² (1.5 MPa) of pressure. Thethermode setpoint was 203° C. When the bonding was finished and thepressure was released, the thermode still maintained the bondingtemperature similar to a steady heater. The details of the glasssubstrate and the chip are described in Table 2.

                  TABLE 2    ______________________________________    Glass Substrate   3M Test Chip    ______________________________________    Material: SiO.sub.2 -coated glass with ITO                      Material: silicon with SiO.sub.2    (indium-tin oxide)                      passivation    Size: 39 × 39 × 1.1 mm                      Size: 6.8 × 6.8 × 0.5 mm    Pitch: 200 micrometer                      Au bump pitch; 200 micrometer    Width of ITO conductor: 100                      Size of bump: 100 × 100 × 25    micrometer        micrometer each    Sheet resistance: 30 ohm/square    ______________________________________

Interconnection resistances were measured using a four-wire methodcommonly used in the art with 0.1 mA DC. In this method, twointerconnections and one aluminum daisy chain (uninterruped claim)resistance were included in the measured value. The data is shown inTABLE 3, below.

                  TABLE 3    ______________________________________             Aging Time    Adhesive Film             (hrs)     Max (ohm)  Ave (ohm)                                         Min (ohm)    ______________________________________    Example   0        4.0        2.2    1.1    Example   24       4.9        2.8    1.3    Example  168       12.9       4.6    1.7    Example  500       19.4       6.8    2.6    Example  1000      36.8       9.7    3.7    Comparative              0        4.7        2.4    1.0    Comparative              24       6.7        3.2    1.1    Comparative             168       13.5       4.7    1.1    Comparative             500       21.6       7.1    2.3    Comparative             1000      83.5       15.5   3.4    ______________________________________

The data of TABLE 3 show interconnection resistances after 1000 hoursaging at 80° C. and 95% relative humidity.

The appearance of the bonds was observed using a microscope withpolarized light. The photomicrographs of FIGS. 1 and 2 show theappearance of the bonds after 1000 hours aging at 80° C. and 95%relative humidity. In both of the FIGS., dendritic structures can beseen. These structures are artifacts of the bonding procedure which donot significantly affect the strength of the bond. The comparativesample depicted in FIG. 2 show that delamination occurred over almostthe whole surface of the chip. This was evidenced by the cloudy ormottled appearance which partially obscured the insignia "3M 120" on thechip. Further, the interconnection resistance had increased considerablyover 1000 hours as shown by the resistance data of TABLE 3. In contrast,the present invention sample, depicted in FIG. 1, showed significantdelamination did not occur. Also, the interconnection resistance wassuperior to that of the comparative sample even after 1000 hours. Thisshowed that the coupling agent of the present invention improved thestability of the bond under humid conditions compared to the comparativecoupling agent.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

We claim:
 1. A composition of matter comprising an aromatic cyanateester silane comprising at least one cyanate ester group and at leastone hydrolyzable silyl group.
 2. The composition of matter according toclaim 1 wherein said cyanate ester silane has the formula

    {(NCO).sub.c --Ar--U'--}.sub.a SiR.sub.b Z.sub.{4-(a+b)}

wherein Ar is selected from the group consisting of a single aromaticring, two or more fused aromatic rings, or two or more aromatic ringsconnected by one of a) carbon-carbon single bonds, b) hydrocarbylgroups, c) ether groups, or d) thioether groups; NCO is a cyanate groupdirectly bound to an aromatic ring of Ar, c=an integer 1 to 5, U' is anorganic group resulting from the hydrosilation of the group U whichcomprises at least one olefinically unsaturated aliphatic orolefinically unsaturated cycloaliphatic group having 2 to 30 carbonatoms directly bound to one of the aromatic rings of Ar, a=an integer inthe range of 1 to 3, R is a nonfunctionalized alkyl or aromatic group,b=0 or 1 or 2, with the proviso that a+b is less than or equal to 3, andZ is a hydrolyzable group capable of reacting with a hydroxyl group. 3.The composition according to claim 2 wherein at least one of c=1 or 2,a=1 or 2, and b=0 or
 1. 4. The composition according to claim 2 whereinAr further comprises at least one non-interfering organic substituent.5. The composition according to claim 2 wherein Ar is selected from thegroup consisting of benzene, naphthalene, 2,2-diphenylpropane, diphenylether, and biphenyl.
 6. The composition according to claim 2 wherein U'comprises at least one non-interfering ether, thioether, ester, or ketolinkage.
 7. The composition according to claim 2 wherein U' is selectedfrom the group consisting of ethylene, propylene, --O--CH₂ --CH₂ --,--O--CH(CH₃)--, --O--CH₂ --CH₂ --CH₂ --, --O--CH₂ --CH(CH₃)--,cyclohexylene, cyclopentylene, --CH₂ --(CH₂)_(x) --CH₂ --CH₂ --, and--CH₂ --(CH₂)_(x) --CH(CH₃)--, wherein x is 1-5.
 8. The compositionaccording to claim 1 wherein said hydrolyzable group is selected fromthe group consisting of halogen atoms and alkoxy groups.
 9. A methodcomprising the steps:reacting an aromatic hydroxyl compound whichcontains at least one aliphatic or cycloaliphatic carbon-to-carbondouble bond withi) cyanogen halide and a base, and ii) a silanecontaining both an Si--H group and a hydrolyzable group, materials ofsteps i) and ii) being reacted in either order, to provide a cyanateester silane compound.